Provide data for more accurate calculation of freed things in the gc.

Rev: src/array.c:1.134
Rev: src/array.h:1.45
Rev: src/mapping.c:1.160
Rev: src/mapping.h:1.48
Rev: src/multiset.c:1.66
Rev: src/multiset.h:1.31
Rev: src/object.c:1.216
Rev: src/object.h:1.76
Rev: src/program.c:1.472
Rev: src/program.h:1.172